In recent years, a solar cell is receiveing an attention as clean energy supplyer, which reflects environmental issues. Therefore, timepieces with their hands driven by energy which is generated by the solar cells and charged into storage units such as secondary batteries, capacitors, and the like are commercially available. Many timepieces having illuminating functions for illuminating the dial by using the EL device which is provided behind the dial are also commercially available.
As a fixing structure for fixing to the timepiece movement the solar cell which supplies power to driving units built into the timepiece movement, a fixing structure is disclosed in WO95/27234, for example.
FIG. 14 is a plan view of a timepiece movement of a conventional timepiece having a solar cell and FIG. 15 is a sectional view taken along line 15--15 in FIG. 14.
As shown in FIGS. 14 and 15, a metal plate 3 is mounted to an upper surface of a timepiece movement 2 which incorporates driving units and a train wheel bridge 4 made of metal is mounted to a lower surface of the timepiece movement 2. A light-transmitting dial 14 formed of transparent or translucent material is disposed above the metal plate 3.
As the driving units built into the timepiece movement 2, there is a stepping motor for moving the hands, for example. The stepping motor is driven by a transmitted signal from a circuit board 6 disposed outside the timepiece movement 2 and moves a second hand 7a, a minute hand 7b, and an hour hand 7c.
The circuit board 6 is supported by a circuit board support 8 made of plastic and provided at a periphery of the timepiece movement 2. Bolts 9 are inserted from a lower surface side of the timepiece movement 2 through the train wheel bridge 4, the circuit board 6, and the circuit board support 8, and the tips of the bolts 9 are screwed into threaded holes in the metal plate 3, thereby fixing the metal plate 3, the train wheel bridge 4, the circuit board 6, and the circuit board support 8 to the timepiece movement 2.
A solar cell 10 for supplying power to the driving units is formed of a metal thin plate and is disposed between the upper surface of the timepiece movement 2 and the circuit board support 8, and the light-transmitting dial 14. A solar cell support frame 11 made of a resin is mounted to a peripheral edge 8a of the circuit board support 8. The solar cell support frame 11 has a first portion 11a projecting from the peripheral edge of the circuit board support 8 toward the timepiece movement 2 and the first portion 11a engages with a peripheral edge of the solar cell 10 without interfering with the dial 14, thereby fixing the solar cell 10 to the circuit board support 8.
FIG. 16 is a partial sectional view of FIG. 14 for explaining conducting means for supplying power from the solar cell 10 to the circuit board 6. As shown in FIG. 16, conductive tape 12 is laminated on a surface of the solar cell 10 and is bonded by thermocompression to a terminal 10a provided to the surface of the solar cell 10 through an anisotropic conductive film. Between the solar cell 10 and the circuit board 6, a leaf spring 13 made of metal is provided to pass through the circuit board support 8 and a end of the leaf spring 13 is in contact with the conductive tape 12. The other end of the leaf spring 13 is bent along the surface of the circuit board 6 to be in contact with a terminal (not shown) of the circuit board 6.
A sectional view of a timepiece according to another prior art of the invention is shown in FIG. 17 for a reference purpose. Differences of this timepiece from one shown in FIGS. 14 to 16 is that power from the solar cell 10 which generates power by receiveing light is supplied to the circuit board 6 via a coil spring 13'. Because the other portions of the timepiece are similar to those in FIGS. 14 to 16, similar reference numerals and characters are provided to the similar portions to omit detailed descriptions of such portions.
FIG. 18 is a partial sectional view showing a state in which the timepiece movement shown in FIGS. 14 to 16 is housed in a case and FIG. 19 is a view taken along line 19--19 in FIG. 18.
As shown in FIGS. 18 and 19, a dial 14 is disposed on the solar cell 10 so as not to interfere with a solar cell support frame 11 and such that a peripheral edge of the dial 14 is positioned on a timepiece movement 2 side. A plurality of (two in the illustrated example) notch portions 14a in U-shape is defined on the peripheral edge of the dial 14 and dial fixing pins 8b defined to project from an upper surface of a circuit board support 8 are press-fitted into and engaged with the notch portions 14a. Thereby, the dial 14 is fixed to the timepiece movement 2 so as not to rotate.
In FIG. 18, a reference numeral 15 indicates the case as an outer member for housing the timepiece movement 2 and the like. An opening in which glass 16 is mounted is formed on an upper surface of the case 15. At a peripheral edge of the opening of the case 15, a parting portion 15a projecting inward is formed and a size of the parting portion 15a defines a range in which the dial 14 can be seen. The parting portion 15a is provided to cover a peripheral edge of the dial 14 from above at the offset place from the dial fixing pins 8b toward a center of the timepiece.
FIGS. 20 and 21 are external views of a timepiece with a conventional solar cell.
As shown in FIGS. 20 and 21, the parting portion 15a is provided to cover the peripheral edge of the dial 14 at the center side of the timepiece offset from the dial fixing pin portions 8b and has a circular shape (FIG. 20) similarly to the dial 14 or a shape of an ellipse (an odd shape) (FIG. 21) slightly smaller than the dial 14.
The above-described conventional timepieces have the following drawbacks. According to the fixing structure of the dial of the conventional timepiece, because an allowable range of the parting portion 15a of the timepiece movement is limited by the dial fixing pins 8b, the parting portion 15a can not be broadened outward from the dial fixing pins 8b and it is difficult to apply a similer design for the timepiece movement to various designs for the timepieces. In other words, if the parting portion 15a of the timepiece is broadened, the solar cell support frame 11 appears at an outer peripheral portion of the dial 14 through the case glass 16 and the tolerance of the parting portion 15a is limited by an inner diameter of the solar cell support frame 11. Therefore, in order to adapt to the various designs, an individual timepiece movement has been conventionally produced on a request for each design. As a result, the cost of producing the timepiece becomes high and production control of the timepiece movements is troublesome because many timepiece movements with various designs are necessary.
It is an object of the present invention to solve the above problems and to provide a timepiece having light-receptive/emitting means such as light-electric power generating means and an EL device, in which a tolerance of a parting portion can be set freely and a timepiece movement fixing structure can meet the various design requests.